/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.view.animation;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.Resources.Theme;
import android.content.res.TypedArray;
import android.graphics.Path;
import android.util.AttributeSet;
import android.util.PathParser;
import android.view.InflateException;
import com.android.internal.R;
/**
* An interpolator that can traverse a Path that extends from <code>Point</code>
* <code>(0, 0)</code> to <code>(1, 1)</code>. The x coordinate along the <code>Path</code>
* is the input value and the output is the y coordinate of the line at that point.
* This means that the Path must conform to a function <code>y = f(x)</code>.
*
* <p>The <code>Path</code> must not have gaps in the x direction and must not
* loop back on itself such that there can be two points sharing the same x coordinate.
* It is alright to have a disjoint line in the vertical direction:</p>
* <p><blockquote><pre>
* Path path = new Path();
* path.lineTo(0.25f, 0.25f);
* path.moveTo(0.25f, 0.5f);
* path.lineTo(1f, 1f);
* </pre></blockquote></p>
*/
public class PathInterpolator extends BaseInterpolator {
// This governs how accurate the approximation of the Path is.
private static final float PRECISION = 0.002f;
private float[] mX; // x coordinates in the line
private float[] mY; // y coordinates in the line
/**
* Create an interpolator for an arbitrary <code>Path</code>. The <code>Path</code>
* must begin at <code>(0, 0)</code> and end at <code>(1, 1)</code>.
*
* @param path The <code>Path</code> to use to make the line representing the interpolator.
*/
public PathInterpolator(Path path) {
initPath(path);
}
/**
* Create an interpolator for a quadratic Bezier curve. The end points
* <code>(0, 0)</code> and <code>(1, 1)</code> are assumed.
*
* @param controlX The x coordinate of the quadratic Bezier control point.
* @param controlY The y coordinate of the quadratic Bezier control point.
*/
public PathInterpolator(float controlX, float controlY) {
initQuad(controlX, controlY);
}
/**
* Create an interpolator for a cubic Bezier curve. The end points
* <code>(0, 0)</code> and <code>(1, 1)</code> are assumed.
*
* @param controlX1 The x coordinate of the first control point of the cubic Bezier.
* @param controlY1 The y coordinate of the first control point of the cubic Bezier.
* @param controlX2 The x coordinate of the second control point of the cubic Bezier.
* @param controlY2 The y coordinate of the second control point of the cubic Bezier.
*/
public PathInterpolator(float controlX1, float controlY1, float controlX2, float controlY2) {
initCubic(controlX1, controlY1, controlX2, controlY2);
}
public PathInterpolator(Context context, AttributeSet attrs) {
this(context.getResources(), context.getTheme(), attrs);
}
/** @hide */
public PathInterpolator(Resources res, Theme theme, AttributeSet attrs) {
TypedArray a;
if (theme != null) {
a = theme.obtainStyledAttributes(attrs, R.styleable.PathInterpolator, 0, 0);
} else {
a = res.obtainAttributes(attrs, R.styleable.PathInterpolator);
}
parseInterpolatorFromTypeArray(a);
setChangingConfiguration(a.getChangingConfigurations());
a.recycle();
}
private void parseInterpolatorFromTypeArray(TypedArray a) {
// If there is pathData defined in the xml file, then the controls points
// will be all coming from pathData.
if (a.hasValue(R.styleable.PathInterpolator_pathData)) {
String pathData = a.getString(R.styleable.PathInterpolator_pathData);
Path path = PathParser.createPathFromPathData(pathData);
if (path == null) {
throw new InflateException("The path is null, which is created"
+ " from " + pathData);
}
initPath(path);
} else {
if (!a.hasValue(R.styleable.PathInterpolator_controlX1)) {
throw new InflateException("pathInterpolator requires the controlX1 attribute");
} else if (!a.hasValue(R.styleable.PathInterpolator_controlY1)) {
throw new InflateException("pathInterpolator requires the controlY1 attribute");
}
float x1 = a.getFloat(R.styleable.PathInterpolator_controlX1, 0);
float y1 = a.getFloat(R.styleable.PathInterpolator_controlY1, 0);
boolean hasX2 = a.hasValue(R.styleable.PathInterpolator_controlX2);
boolean hasY2 = a.hasValue(R.styleable.PathInterpolator_controlY2);
if (hasX2 != hasY2) {
throw new InflateException(
"pathInterpolator requires both controlX2 and controlY2 for cubic Beziers.");
}
if (!hasX2) {
initQuad(x1, y1);
} else {
float x2 = a.getFloat(R.styleable.PathInterpolator_controlX2, 0);
float y2 = a.getFloat(R.styleable.PathInterpolator_controlY2, 0);
initCubic(x1, y1, x2, y2);
}
}
}
private void initQuad(float controlX, float controlY) {
Path path = new Path();
path.moveTo(0, 0);
path.quadTo(controlX, controlY, 1f, 1f);
initPath(path);
}
private void initCubic(float x1, float y1, float x2, float y2) {
Path path = new Path();
path.moveTo(0, 0);
path.cubicTo(x1, y1, x2, y2, 1f, 1f);
initPath(path);
}
private void initPath(Path path) {
float[] pointComponents = path.approximate(PRECISION);
int numPoints = pointComponents.length / 3;
if (pointComponents[1] != 0 || pointComponents[2] != 0
|| pointComponents[pointComponents.length - 2] != 1
|| pointComponents[pointComponents.length - 1] != 1) {
throw new IllegalArgumentException("The Path must start at (0,0) and end at (1,1)");
}
mX = new float[numPoints];
mY = new float[numPoints];
float prevX = 0;
float prevFraction = 0;
int componentIndex = 0;
for (int i = 0; i < numPoints; i++) {
float fraction = pointComponents[componentIndex++];
float x = pointComponents[componentIndex++];
float y = pointComponents[componentIndex++];
if (fraction == prevFraction && x != prevX) {
throw new IllegalArgumentException(
"The Path cannot have discontinuity in the X axis.");
}
if (x < prevX) {
throw new IllegalArgumentException("The Path cannot loop back on itself.");
}
mX[i] = x;
mY[i] = y;
prevX = x;
prevFraction = fraction;
}
}
/**
* Using the line in the Path in this interpolator that can be described as
* <code>y = f(x)</code>, finds the y coordinate of the line given <code>t</code>
* as the x coordinate. Values less than 0 will always return 0 and values greater
* than 1 will always return 1.
*
* @param t Treated as the x coordinate along the line.
* @return The y coordinate of the Path along the line where x = <code>t</code>.
* @see Interpolator#getInterpolation(float)
*/
@Override
public float getInterpolation(float t) {
if (t <= 0) {
return 0;
} else if (t >= 1) {
return 1;
}
// Do a binary search for the correct x to interpolate between.
int startIndex = 0;
int endIndex = mX.length - 1;
while (endIndex - startIndex > 1) {
int midIndex = (startIndex + endIndex) / 2;
if (t < mX[midIndex]) {
endIndex = midIndex;
} else {
startIndex = midIndex;
}
}
float xRange = mX[endIndex] - mX[startIndex];
if (xRange == 0) {
return mY[startIndex];
}
float tInRange = t - mX[startIndex];
float fraction = tInRange / xRange;
float startY = mY[startIndex];
float endY = mY[endIndex];
return startY + (fraction * (endY - startY));
}
}
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